1. Field of the Invention
The present invention relates to a thermoplastic material comprising a vulcanized rubber in a subdivided form.
In particular, the present invention relates to a thermoplastic material comprising a vulcanized rubber in a subdivided form and at least one heterophase copolymer comprising a thermoplastic phase made from a propylene homopolymer or copolymer and an elastomeric phase made from a copolymer of ethylene with an α-olefin.
The present invention moreover relates to a manufactured product comprising said thermoplastic material.
2. Description of the Related Art
The increased production of industrial rubber products has resulted in the accumulation of large amounts of rubber wastes which per se do not find any practical applications and are generally disposed in dedicated landfills with the main drawbacks of environment pollution as well as of the need for large dedicated areas for storing said wastes.
It is known in the art to depolymerize waste stream of rubber, such as tyres, in an effort to reduce the volume of waste and obtain a useful byproduct. Likewise, rubber product may be devulcanized in an attempt to recycle the waste rubber.
In addition to these techniques, it is common in the art to grind the waste streams of rubber and utilize the ground particles so obtained. These ground particles are then typically compounded with other polymeric materials in order to make final product which may be employed in a plurality of applications.
However, it has been found that the addition of such ground rubber particles to the polymeric material results in a significant deterioration of the mechanical properties of the resulting polymeric composites.
Many efforts have been made in the art in order to overcome the above reported problems.
For example, patent U.S. Pat. No. 5,010,122 relates to thermoplastic compositions comprising rubber particulate having a size less than about 10 mesh, a thermoplastic material, and at least one coupling agent. The thermoplastic material preferably comprises an olefin, a co-polymer of an olefin, a homopolymer of an olefin, or blends thereof. The coupling agent preferably comprises a silane coupling agent. The abovementioned thermoplastic compositions are said to have excellent physical properties.
Patent U.S. Pat. No. 5,157,082 relates to thermoplastic compositions comprising mixtures of ground vulcanized rubber, polyolefin resin, and at least one functionalized olefin polymer which may be selected from a copolymer of at least one olefin and at least one ethylenically unsaturated organic monomer. The polyolefin resin is a solid, high molecular weight polymeric material made by polymerizing one or more olefinic monomers in a conventional manner. Preferred polyolefin resins are polyethylene or polypropylene. Also suitable for the practice of the invention are copolymers of two or more olefins with copolymers of ethylene and propylene being preferred. The abovementioned thermoplastic compositions are said to have improved mechanical properties.
Patent U.S. Pat. No. 5,889,119 relates to a thermoplastic rubbery composition comprising (I) from about 10 to about 40 parts by weight of a low-modulus binder including: (a) from about 75 to about 25 parts by weight of a crystalline polyolefin resin, and (b) from about 25 to about 75 parts by weight of a binder rubber in the form of particles having an average diameter of less than about 20 μm, said binder rubber having been dynamically vulcanized; and (II) from about 90 to greater than 50 parts by weight of ground vulcanized rubber particles having an average diameter in the range of from about 50 μm to about 1.2 mm. The polyolefin resins are preferably high density polyethylene or polypropylene. The abovementioned thermoplastic rubbery composition is said to have improved physical properties.
U.S. Pat. No. 6,015,861 relates to a method of preparing a rubber-blend thermoplastic composition, comprising the steps of: (a) providing a ground crosslinked rubber having an average particle size of about 80 mesh or smaller; and (b) combining the ground crosslinked rubber with a thermoplastic polyolefinic material and a compatibilizer based on a paraffinic oil to form a blend thermoplastic resin composition. The preferred thermoplastic polyolefinic material are polyethylene, polypropylene, ethylene copolymers, propylene copolymers, poly(ethylene propylene)copolymers, and mixtures thereof. The composition prepared by the abovementioned method is said to include a surprisingly high level of recycle rubber without adverse effect on its physical or aesthetic properties.
U.S. Pat. No. 6,031,009 relates to thermoplastic compositions comprising a blend of ground vulcanized rubber, at least one conventional olefin polymer and at least one metallocene single site catalyzed α-olefin copolymer. The olefin polymer is a solid, high molecular weight polymeric material made by polymerizing one or more olefinic monomers in a conventional manner. Preferred olefin polymers are polyethylene or polypropylene. The abovementioned thermoplastic compositions are said to have improved mechanical properties.
International Patent Application WO 00/78852 relates to a method for producing an elastomeric alloy similar to thermoplastic elastomers using reclaimed or waste rubber. To this end, a polypropylene copolymer or a mixture thereof with at least one polypropylene type, is melted in a mixer. Subsequently, powdered rubber, at least a part of which is pre-swollen in a radical donor, is added to the melt in a metered quantity, the powdered rubber is dispersed in the plastic matrix by applying high shear forces whilst adding radical-forming agents in accordance with defined mixing parameters to produce a phase coupling between the powdered rubber and the polypropylene copolymer or a mixture thereof. The obtained elastomeric alloy is said to have properties similar to thermoplastic elastomers.
U.S. Pat. No. 6,262,175 relates to a thermoplastic composition containing, in percentages by weight based on the total weight of the composition: about 5% to about 90% of vulcanized rubber crumb; about 5% to about 60% polyolefin; about 2% to about 30% uncured rubber or styrene-based thermoplastic elastomer; and about 2% to about 30% vinyl polymer selected from vinyl homopolymers, copolymers and mixtures thereof. The polyolefin is a solid, high molecular weight polyolefin homopolymer or copolymer, or mixtures thereof. Preferred polyolefin are polyethylene, polypropylene, or a copolymer of ethylene and propylene. The abovementioned thermoplastic composition is said to have excellent physical properties, including excellent ultimate elongation and tear strength.
International Patent Application WO 02/24795 relates to a method for recycling a thermoset rubber material comprising subjecting a recycled thermoset rubber material to a phase compatibility treatment with an oxidizing agent and blending the recycled thermoset rubber material with a thermoplastic polymer to obtain a material selected from the group consisting of a thermoplastic elastomer and an impact-strengthened thermoplastic. Polyolefins (e.g. polypropylene) are among the more preferred thermoplastic polymers.